Polysiloxane lubricant compositions



United States Patent 3,090,754 POLYSILOXANE LUBRICANT COMPOSITIONS Harry M. Schiefer, Midland, Mich., assignor to DOW Corning Corporation, Midland, Mich., a corporation of Michigan No Drawing. Filed Feb. 26, 1958, Ser. No. 717,574 2 Claims. (Cl. 25249.7)

This invention relates to lubricants comprising mixtures of bromophenysiloxanes and certain organotin compounds.

It is known from US. Patent 2,599,984 that siloxanes containing halogenated phenyl radicals are superior to hydrocarbon substituted siloxanes for lubrication of moving metallic parts. However, with the continuing demand for lubricants which are operated at increasingly high temperatures and under heavy load, it has been found that the halogenated phenylsiloxanes heretofore employed were not suitable for many of the more extreme conditions under which lubrication is required.

It is the object of this invention to provide new siloxane compositions which give superior lubricity without sacrificing the other desirable properties of siloxane lubricants such as low freezing point, high temperature stability and relatively small changes in viscosity with temperature. Other objects and advantages will be apparent from the following description.

This invention relates to compositions of matter comprising 1) a fluid copolymeric siloxane having both dibromophenyl and methyl radicals attached to the silicon atoms thereof, any remaining organic radicals attached to the silicon atoms in said copolymer being phenyl radicals, in said siloxane at least 50% of the total organic radicals being methyl and the dibromophenyl radicals being present in amount such that there is from 6 to 25% by weight bromine in the copolymer and (2) a tin compound of the group consisting of polymers of the unit formula R: R; R2 Sl0H2S11CHzSlO copolymers of the unit formula R2 R's R2 R2 R2 SiOHzSnCH2SiO (SiOHzCHzSiO) n and compounds of the formulae [R SIIR SHR' and in which tin compounds R is phenyl or methyl, n is an integer of at least 1 and R is an alkyl radical of less than 6 carbon atoms or a phenyl radical, (2) being present in amount such that there is from .5 to 2% by weight tin in the combined Weights of (l) and (2).

For the purpose of this invention, siloxanes 1) employed in this invention are copolymeric fluid siloxanes containing both dibromophenylsiloxane units and methyl siloxane units. The dibromophenylsiloxane units can be any of the following: mono-dibromophenylsiloxane,

(i.e. Bra

SiOm) dibromophenylmethylsiloxane,

(i.e. Bra

dibromophenyldimethylsiloxane, dibromophenylphenylsiloxane, dibromophenyldiphenylsiloxane and dibromophenylphenylmethylsiloxane. For the purpose of this invention the position of the bromine atoms relative to the silicon is not critical. For example, the bromine atoms 2 can be in the 2, 3 positions, the 2, 4 positions, the 2, 5 positions, the 2, 6 positions, the 3, 4 positions or the 3, 5 positions.

The remaining siloxane units in the copolymer can be of the following types: monomethylsiloxane, dimethylsiloxane, trimethylsiloxane, monophenylsiloxane, diphenylsiloxane, triphenylsiloxane, phenylmethylsiloxane, phenyldimethylsiloxane and diphenylmethylsiloxane. These units can be present in any combination provided that the resulting copolymer is a fluid and provided that at least 50% of the total number of organic radicals (that is the total number of methyl plus phenyl plus dibromophenyl radicals) are methyl radicals. It has been found that inferior lubrication takes place when the amount of dibromophenyl radicals in the copolymer is such that the percent by weight bromine is less than 6 and more than 25 Dibromophenylsiloxanes are best prepared by brominating phenyltrichlorosilane with elemental bromine in the presence of an iron catalyst to give dibromophenyltrichlorosilane. If it is desired to place phenyl or methyl groups on the same silicon with the dibromophenyl group this is best done by reacting the dibromophenyltrichlorosilane with the corresponding Grignard reagents. The copolymers of this invention are best prepared by cohydrolyzing the dibromophenylchlorosilanes with methyland phenylchlorosilanes.

The tin compositions of this invention 2) can be homopolymeric compounds of the unit formula R; R, R1 SiOH:SnCH2SiO These compounds are best prepared 'by reacting at a temperature below 40 C. a dialkyltindihalide of the formula R' SnX with a Grignard reagent of the formula R; R; R --SiCH2S11CH2SiO- and units of the formula R2 R2 -SlCH2OH2SiO- These copolymers can be prepared by carrying out the reaction between Mg and R2 R2 XCHzSiOSiCHaX under conditions which cause intermolecular condensation of the Wurtz type to produce polymers of the formula R2 R2 R2 R2 XMgCHgSflOSiCHaOH2SflnOSiOHzMgX where n is an integer of at least 1. This intermolecular condensation is best obtained by carrying out the reac-v tion at temperatures above 40 C. These polymers are then reacted with the dialkyltindihalide to give copolymers having varying ratios of admixture of any number of species.

The tin compounds (2) can also be monomeric materails of the formula [R SiCH SnR' and These compounds are best prepared by reacting Grignard reagents of the formulae R siCH MgX or R siosioHzMgX respectively, with a dialkyltindihalide. In addition, the monomeric tin compounds can have the formula ethyl, propyl, isopropyl, butyl, secondary butyl, tertiary butyl and amyl.

The dialkyltindihalides employed in the production of the compositions of this invention are commercially available materials. 7

The compositions of this invention are prepared by merely mixing ingredients (1) and (2). In order to obtain the superior lubricity of this invention compound (2) should be employed in amount such that the percent by weight tin in the combined weights of (1) and (2) is from 0.5 to 2% inclusive. It should be understood, of course, that a mixture of two or more of the above-defined tin compounds can be employed in any composition.

The compositions of this invention are particularly useful for the lubrication of moving metallic parts in hydraulic. pumps. Their superiority over other siloxane lubricants is particularly evident at high loads. They can be employed either per se as fluids or they can be first thickened to produce greases.

The compositions of this invention can be thickened into greases with any of the conventional thickening agents which are employed with siloxane greases. These include carbon black, lithium salts of carboxylic acids such as lithium stearate and lithiurn-12-hydroxystearate; alkali metal and alkaline earth metal salts of alicyclic substituted fatty acids such as cyclohexylacetic, cyclohexylpropionic, cyclohexylbutyric, gamma ethylcyclohexylbutyric, alpha 4- ditertiarybutylcyclohexylbutyric, 2-cyclohexenecaproic, pentalaneacetic and eyclophenylvaleric; substituted ureas of the formula YNHCONHY in which Y is an alkyl-radical such as methyl, ethyl or octadecyl; aryl ureas of the formula YNHCONHY where Yis-an aryl radical such as phenyl, tolyl and xenyl and aryl-carbamyl compounds melting above 25 C. such as compounds of the formula YCONHY and Y-NHCONHYNHCO-NHY in which Y is an aryl radical such as phenyl, tolyl, and xenyl and Y is an arylene radical such as phenylene and xenylene.

The greases made from the compositions of this invention can be compounded in accordance with any of the conventional methods used for making silicone greases.

In addition to-thickening agents the greases of this invention may contain other ingredients normally added to siloxane lubricants such as oxidation inhibitors.

'Ihelubricating qualities of the compositions shown in the following examples were all determined on the 'Shell 4-ball wear testing machine. In this test a /2 inch steel ball is rotated against three stationary /2 inch steel balls at .a rate of 1200 1'.p.m. at a temperature of 400 F. under a load of 40 "kilograms for 2 hours. At the end of this time the length and width of the scar formed'on each stationary ball is determined and the average of these six measurements is taken as the scar diameter and reported in millimeters.

The following examples are illustrative only and should not be construed as limiting the invention which is properly delineated in the appended claims. In the following examples and claims the following abbreviations are used: Me for methyl, Bu for butyl and Ph for phenyl.

Example 1 This example shows the superiority of the compositions of this invention as antiwear and high pressure lubricants for sliding steel surfaces over dibromophenylsiloxane containing fluids which have no tin additives and over the corresponding chlorophenyl fluids which contain an identical tin additive. Each of the compositions shown below contain 3% by weight of a fluid containing 18.9% by;

weight tin. This fluid was a mixture of copolymers composed of units of the formulae Each composition was tested on the Shell 4-ball tester as shown above and the results-were as follows.

Composition: Scar diameter in mm. Blank 2 1 1.2 2 1.35 3 .9

1 Identical with composition -3 except that no tin additive was present.

Example 2 The tin additive employed in this example was made by reacting dimethyltindichloride with the reaction product of magnesium and ClCI-I SiMe OSiMe CH Cl. The resulting product contained 24.55% by weight tin indicating that it was a mixture of copolymers containing units of the formula Men. Me: Me: ME: Me; -SiOHzSnCH i0 and SiCHZCHflSiO in the approximate ratio of 1:1.

3% by weight of this tin copolymer was added to a 50 cs. fluid copolymer of 15 mol percent trimethylsiloxane, 81.3 mol percent dimethylsiloxane and 3.7 mol percent mono-dibromophenylsiloxane. The resulting mixture was tested for lubricity as shown above and the scar diameter was .89 mm.

Example 3 Each of the following tin compounds was added to the siloxane copolymer fluid of Example 2 in the amounts indicated and the lubricity'of the mixture was determined by the above test. The results were as follows:

Percent by wt. of tin com- Scar pound based on total Formula of tin compound diamete wt. of siloxane and tin inmm. compound MesSiOlzSnBllz 1. 00 MeaSiCHflzSllBllz -4. 1. O7 PhMezSiCHzhSnMGz 86 4 [MeaSiOSiCHghSnMez .94

Example 4 3% by weight of a copolymeric tin compound having units of the formula M82 Bug Me:

SiCHz SnOH2 S 10 and units of the formula Me: Me:

SiCHzOHzSiO which copolymer contained 18.9% by weight tin, was mixed with a 161 cs. fluid copolymer of a composition 8 mol percent mono-dibromophenylsiloxane, 77 mol percent dimethylsiloxane and 15 mol percent trimethylsiloxane. The mixture was tested as shown above and the scar diameter was found to be .99 mm.

Example 6 Equivalent results are obtained when 3% by weight of the following tin compounds are used in the siloxane fluid of Example 2:

P112 Meg Phg SiCH2SnCH2Si Equivalent results are obtained when a mixture of 3% by weight [Me SiCH SnMe and 97% by weight of a siloxane copolymer fluid of the composition 5 mol percent dibromophenylmethylsiloxane, 5 mol percent diphenylsiloxane, 1 mol percent monomethylsiloxane, 10 mol percent phenyldimethylsiloxane and 79 mol percent dimethylsiloxane is employed as a lubricant for steel surfaces.

That which is claimed is:

1. A composition of matter consisting essentially of 1) a fluid copolymeric silox-ane having dibromophenyl and methyl groups attached to the silicon atoms thereof, there being no more than one dibromophenyl radical attached to any one silicon atom, any remaining organic radicals attached to the silicon atoms in said copolymer being phenyl, in said copolymer at least of the total organic radicals being methyl and the dibromophenyl radicals being present in amount such that there is from 6 to 25% by weight bromine in the copolymer and (2) a tin compound selected from the group consisting of polymers of the unit formula R: R: R2 SiCH2SnOH2SiO copolymers of the unit formula R2 R: R2 R: R: -SiCHaSD.CHzSiO[SiCHgCHgSiOlu and compounds of the formulae [R SiCH SnR' and [R SiO] SnR' in which tin compounds R is selected from the group consisting of phenyl and methyl radicals, n is an integer of at least 1 and R is of the group consisting of phenyl and alkyl radicals of less than 6 carbon atoms, (2) being present in amount such that there is from .5 to 2% by weight tin in the combined Weights of (1) and (2).

2. A composition in accordance with claim 1 wherein the copolymeric siloxane is a copolymer of monodibromophenylsiloxane, dimethylsiloxane and tritnethylsiloxane and the tin compound is of the formula where n has a value from 0 to 10 inclusive and Me is methyl.

References Cited in the file of this patent UNITED STATES PATENTS 2,599,984 Fletcher et al June 10, 1952 2,937,994 Holdstock May 24, 1960 2,937,995 Holdstock et a1 May 241 1960 

1. A COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF (1) A FLUID COPOLYMERIC SILOXANE HAVING DIBROMOPHENYL AND METHYL GROUPS ATTACHED TO THE SILICON ATOMS THEREOF, THERE BEING NO MORE THAN ONE DIBROMOPHENYL RADICAL ATTACHED TO ANY ONE SILICON ATOM, ANY REMAINING ORGANIC RADICALS ATTACHED TO THE SILICON ATOMS IN SAID COPOLYMER BEING PHENYL, IN SAID COPOLYMER AT LAST 50% OF THE TOTAL ORGANIC RADICALS BEING METHYL AND THE DIBROMOPHENYL RADICALS BEING PRESENT IN AMOUNT SUCH THAT THERE IS FROM 6 TO 25% BY WEIGHT BROMINE IN THE COPOLYMER AND (2) A TIN COMPOUND SELECTED FROM THE GROUP CONSISTING OF POLYMERS OF THE UNIT FORMULA 